Asteroid Image

This is a composite color image produced by combining the g, r and i filter images which are color coded as blue, green and red respectively. A few ordinary stars are seen as orange and white-blue dots. The two extended yellow objects near the bottom of the image are galaxies. The three blue, green and red dots near the center are the detections of an asteroid. Since the asteroid was at a different position when each of the three frames were taken, it appears as three stars with very unnatural colors. The distance between the red and blue dot is three times as large as the distance between the green and red dot because the time between the exposures in the i and g bands is three times as large (216 seconds) as the time between the r and i exposures (72 seconds). This motion is a give-away sign that is used to distinguish asteroids from stationary stars.
Image credit: Tom Quinn and Zeljko Ivezic, SDSS Collaboration

This image is also available as a 60 dpi GIF (588 x 600, 20 KB).

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